1. Field of the Invention
The invention relates to a chip, more particularly to a transformation chip for a ribbon microphone.
2. Description of the Related Art
Conventional acoustoelectric microphones (MICs) are classified into three categories, namely, condenser MICs, piezoelectric MICs, and ribbon MICs.
A condenser MIC is characterized in that a deformable diaphragm vibrated by an external sound wave is a condenser. The change in capacitance of the condenser during vibration is transformed into small voltages corresponding to the sound wave. The small voltages are amplified and outputted as electric signals for subsequent operation of the condenser MIC. A piezoelectric MIC is characterized in that a diaphragm activated by an external sound wave is made of a piezoelectric material such as quartz. The diaphragm deformed by the sound wave can generate voltages by virtue of inherent piezoelectric properties, thus transforming the sound wave into voltage signals for subsequent operations in the piezoelectric MIC.
Referring to FIGS. 1 and 2, a conventional ribbon MIC 1 comprises a housing 11, a set of magnetism devices 12 disposed in the housing 11 to generate a magnetic field along a direction 100, and a diaphragm 13 that can respond to an external sound wave and deform accordingly. A conductive voice coil 14 is disposed on the diaphragm 13 to interact with the magnetic field. When the diaphragm 13 vibrates in response to a sound wave, the voice coils 14 segment magnetic lines of force and thereby generate induced currents as electric signals for subsequent operation. In practice, the larger the number of magnetic lines of force segmented by the voice coils 14, the higher will be the induced current that is generated, and the better will be the sensitivity of the MIC 1. Consequently, the diaphragm 13 and the voice coil 14 are usually designed to have a corrugated configuration.
Acoustoelectric transformation in a ribbon MIC 1 relies on the vibration of the diaphragm 13 in response to the soundwave that pushes the voice coil 14. Generally, a lighter weight of the diaphragm 13 and a finer size of the voice coil 14 facilitate sensing of weak sound waves and ceasing and repeating movements of the diaphragm 13 and the voice coil 14 within a short time, that is to say, the better the sensitivity of the MIC 1, the better will be the frequency response characteristics.
However, the weights and sizes of the diaphragm 13 and the voice coil 14 are limited by the conventional fabrication process of the conventional ribbon MIC 1, particularly, by mechanical processing steps that produce the diaphragm 13 and the voice coil 14. Therefore, the diaphragm 13 and the voice coil 14 of the conventional ribbon MIC 1 cannot be reduced in weight and size, and the signals generated therefore tend to attenuate at high and low frequencies.
In Taiwanese Publication No. 200845799 and No. 200845800, methods using techniques of semiconductor fabrication and microelectromechanical system (MEMS) to manufacture an acoustoelectric chip package for a ribbon MIC including micro-sized diaphragm and voice coil are proposed. However, since the total length of a voice coil to be displaced in a magnetic field is also an important parameter, there is still a need for increasing the total length of a voice coil for an acoustoelectric chip package of a ribbon MIC.